A common genetic polymorphism of Apo A-IV, Apo A-IV-2, has been identified, and recent work by the principal investigator has established that Apo A-IV-2 displays unique structural and functional characteristics which may cause a distinctive and salutary response to dietary cholesterol in individuals heterozygous for the mutant gene. The principal investigator has also completed a recent study investigating the effect of the Apo A-IV-2 allele on the response of serum lipids and apolipoproteins to high cholesterol diets.